Enhanced excitability of guinea pig ileum myenteric AH neurons during and following recovery from chemical colitis

Inflammation of the colon changes motor function of more proximal regions of the gastrointestinal tract. Colitis alters the neurophysiology of enteric neurons within the region of inflammation, which may contribute to altered colonic motor and secretory function. This study seeks to test the hypothesis that colitis alters the neurophysiology of myenteric neurons in the non-inflamed ileum, and that altered neurophysiology coincides with altered small bowel motor function. Trinitrobenzene sulfonic acid (TNBS)-induced colitis was associated with hyperexcitability of AH neurons in the ileum myenteric plexus, demonstrated by depolarized neurons and increased numbers of action potentials, but without changes in the action potential duration or afterhyperpolarization typical of plasticity in these cells. There were no changes in synaptic transmission of either AH neurons or S neurons observed in the current study. The onset of AH neuron hyperexcitability occurred 24 h following administration of TNBS, and persisted to eight weeks, a time point following the resolution of colitis. Small bowel transit was reduced as early as 12 h after TNBS and resolved by 48 h after TNBS. While AH neurons play a central role in coordinating motor function of the ileum, changes in excitability of these neurons did not coincide with changes in small bowel transit.